1. Field of the Invention
The invention relates to a cooling system, and more particularly, to a cooling system that cools a heat generation source using a vapor compression refrigeration cycle.
2. Description of Related Art
As a measure against environmental issues, hybrid vehicles, fuel cell vehicles, electric vehicles and the like, which run by a driving force of a motor, have been drawing attention. In each of such vehicles, electric apparatuses such as a motor, a generator, an inverter, a converter, a battery and the like generate heat by giving/receiving electric power. Therefore, these electric apparatuses need to be cooled. Thus, there has been proposed an art of cooling a heating element using a vapor compression refrigeration cycle that is employed as a vehicular air conditioner.
For example in Japanese Patent Application Publication No. 2007-69733 (JP-2007-69733 A), there is described a system that cools a heating element using a refrigerant for an air conditioner. In this system, a heat exchanger that exchanges heat with air-conditioning air, and a heat exchanger that exchanges heat with the heating element are arranged in parallel with each other in a refrigerant passage that extends from an expansion valve to a compressor. Further, in Japanese Patent Application Publication No. 2005-90862 (JP-2005-90862 A), there is described a cooling system. In this cooling system, heating element cooling means for cooling a heating element is provided in a bypass passage that bypasses a compressor, an evaporator, and a pressure reducer of an air-conditioning refrigeration cycle.
On the other hand, with regard to a vehicular air-conditioning system, in Japanese Patent Application Publication No. 2003-285633 (JP-2003-285633 A), there is described a device that causes a refrigerant to pass through a cold storage heat exchanger having a cooling storage material during the operation of a compressor, and cools the refrigerant by stored cold energy of the cooling storage material to operate an air conditioner after the stoppage of the compressor. In Japanese Patent Application Publication No. 2011-1048 (JP-2011-1048 A), there is described a vehicular air-conditioning system. In this vehicular air-conditioning system, a heat storage medium of an in-vehicle heat storage unit stores a quantity of heat, and the in-vehicle heat storage unit exchanges the quantity of heat with a heat exchange medium.
In the cooling system described in each of Japanese Patent Application Publication No. 2007-69733 (JP-2007-69733 A) and Japanese Patent Application Publication No. 2005-90862 (JP-2005-90862 A), a cooling path for cooling a heat generation source such as an electric apparatus or the like is incorporated in a vapor compression refrigeration cycle. When the heat generation source is cooled, the refrigerant in a two-phase state, namely, a gas-liquid phase state is introduced into a refrigerant path for cooling the heat generation source after having passed through a pressure reducer. When the flow rate of the refrigerant for cooling the heat generation source decreases, the performance of cooling the heat generation source may deteriorate.